Mechanism of Action of the Pore-Forming Lectins Mediated by Binding to Cell Surface Carbohydrate Chains

Abstract

Protein toxins damage target cells using a highly efficient process that involves specific interactions with membrane lipids. Some bacterial protein toxins form membrane-penetrating pores by oligomerizing in the cell membrane after binding to target cells, leading to cell death. Similar mechanisms of pore formation are involved in the action of hemolytic lectins from eukaryotes. A hemolytic lectin isolated from the sea cucumber Cucumaria echinata was characterized in the terms of its carbohydrate-binding and oligomerization abilities. Structural analyses of the monomeric and oligomeric forms of this lectin revealed large conformational changes during the pore-formation process. These changes exemplify the remarkable structural transition of proteins caused by protein–carbohydrate as well as protein–lipid interactions on the cell surface.